1. Field of the Invention
This invention relates in general to means and methods for controlling the amount of a volatile reactant derived from a solid or liquid source and sent to a reaction vessel, and more particularly, to improved means and methods for supplying such a reactant in a highly uniform and reproducible manner in connection with the manufacture of electronic devices.
2. Background Art
Solid and liquid reactant sources are widely used in the manufacture of electronic devices, particularly semiconductor devices. They are used in connection with formation and/or doping of many types of layers or regions, as for example; amorphous, polycrystalline, or epitaxial semiconductor layers; dielectric layers of many compounds; metal and semimetal conductor layers; and doped semiconductor regions. The reactant derived from the solid or liquid source may form the entire layer, or become one constituent of a compound layer, or be provided as a dopant to a pre-existing layer or region, or a combination thereof. A typical example of the use of liquid sources, is the use of silicon bearing compounds, such as tri-chlorosilane and/or silicon tetra-chloride which are liquid at ordinary temperatures, as sources of silicon for the growth of silicon layers on semiconductor wafers. A typical example of the use of a solid source, is the use of various solid boron compounds, such as boron glasses or ceramics, as a source of boron for doping of semiconductor wafers or layers.
A common problem in reactions systems using liquids or solids as a source for a reactant, is achieving a high degree of uniformity and reproducibility of the reaction rate. For example, in silicon epitaxial reactors wherein the silicon is derived from tri-chorosilane or silicon tetra-chloride, it has not been possible to achieve a high degree of run-to-run reproducibility of layer growth rate and/or terminal thickness. This is due to the fact that there are many variables in the system, as for example, source temperature, gas flow rate, reactor pressure, and the like, which have an effect on the amount of the reactant which is transported from the source material into the reaction chamber where epitaxial deposition occurs. While one could, ideally, obtain more uniform layer growth and repeatability by precisely regulating these and other variables, in practice this has not been practical, particularly with high throughput, volume production, systems. It is highly desirable to be able to more closely regulate and reproduce layers, films, doped regions, etched regions, and the like, which depend on the use of liquid or solid sources of reactants. Thus, a need continues to exist for improved means and methods for deriving one or more reactants from liquid and/or solid sources and transporting them to a reaction chamber in a very uniform and reproducible manner.
Accordingly, it is an object of the present invention to provide an improved method for deriving reactants from liquid or solid sources and transporting them to a reaction chamber, particularly in arrangements employing a carrier gas.
It is a further object of the present invention to provide an improved means and method for controlling the flow of a reactant derived from a liquid or solid source into a reaction vessel in a highly uniform and reproducible manner.
It is a still further object of the present invention to provide an improved means and method for uniformly and reproducibly forming layers on semiconductor devices.
It is an additional object of the present invention to provide an improved means and method for uniformly and reproducibly doping and/or etching semiconductors.
It is a yet additional object of the present invention to achieve the above noted objectives in systems suited to high throughput volume manufacturing.